This study examines mechanisms of alloimmune injury to vascular endothelium and smooth muscle. Using radiolabeled cell surface proteins from cultured cells, the surface proteins of endothelium and smooth muscle are compared to those of T- and B-lymphocytes, monocytes, platelets and erythrocytes by one- and two-dimensional electrophoresis. By immunoprecipitation with monospecific sera, protein patterns of known histocompatibility antigens will be defined. Immune transplant recipient sera will then be used to precipitate surface antigens from labeled lysates of endothelium and smooth muscle, looking in particular for antigens unique to endothelium/monocytes or smooth muscle. Sera showing such unique specificities will be identified for use in endothelial and smooth muscle cell tissue typing. The capacity of smooth muscle cells to stimulate a lymphocyte proliferative response and to function as a target for complement-dependent cytotoxic antibody, antibody-dependent cell mediated cytolysis and direct cell mediated will be compared with similar capacities of autologous endothelium and lymphocytes.